Comets originally form as balls of ice and rock in the Kuiper Belt and Oort Cloud

Objects orbiting in the Kuiper Belt and Oort Cloud are mainly composed
of rock, ice, ammonia and methane.

When objects from the Kuiper Belt and Oort Cloud enter the inner solar system they become comets due to interactions with the sun.

There are thought to be at least 70,000 objects in the Kuiper Belt with
a diameter over 62 miles (100 km).

The dwarf planets Pluto, Eris, MakeMake and Haumea all orbit in the
Kuiper Belt.

The Kuiper Belt is named after the Dutch astronomer Gerard Kuiper.

There are possibly 2 trillion icy bodies in the Oort Cloud.

The Oort Cloud extends so far it almost reaches a quarter way to the nearest
star Proxima Centauri.

Objects found in the Oort Cloud are believed to be remnants from the
early formation of the solar system that were thrown far into space
by the gravity of the giant planets.

The Oort Cloud is named after another Dutch astronomer Jan Hendrik Oort.

The Oort Cloud is composed of icy objects which surrounds the solar system

The Kuiper Belt

The Kuiper Belt is located at around 2.8 billion miles
(4.5 billion km) from the sun and extends several
billion miles. It is similar to the
asteroid belt except it is around 20 times larger, and
instead of being primarily composed of rocks objects found here also contain
methane, ammonia and ice.

The Oort Cloud

The Oort Cloud begins at 750 billion km from the sun and
ends at the very edge of our solar system, almost 1
light year from the sun. It is a massive spherical
cloud containing billions of icy bodies. Occasionally
these bodies get knocked out of their orbit and enter
the inner solar system, they then become comets.
Although some comets originate from the Kuiper Belt most
come from the Oort Cloud.

Comets

Comet Bombardment of Early Earth

Comets are icy bodies from the Kuiper Belt and Oort Cloud which enter the
inner solar system. Comets originating from the Kuiper belt have short
orbital periods below 200 years, bodies from the Oort Cloud have orbits
ranging from 200 years up to millions of years. When these icy objects enter
the inner solar system the effects of solar winds and radiation vaporizes
the ice creating a thin atmosphere around them known as a coma, occasionally
they will also develop a tail.

It is believed that the gravitational pull of the outer planets bring bodies
from the Kuiper Belt into the inner solar system. Objects in the Oort Cloud
are effected by giant molecular clouds or passing stars that can nudge them
out of their orbit. As comets cross the orbital paths of planets they do
occasionally collide with them, as was the case in 1994 when fragments of
Comet Shoemaker-Levy 9 hit Jupiter.

Comets are extremely important in the development of planets as they possess vital volatile elements, including most importantly water. In its early life planet Earth was bombarded by comets, creating liquid water oceans on its surface, without this event it is possible that life may not have developed on our planet.

Comet Missions

There has already been several stunningly successful missions to study comets,
Giotto in 1986 studied Halley’s Comet and then went on to make a close pass of
Grigg-Skjellerup in 1992. Stardust captured comet dust from Comet Wild 2 in 2004
and returned those samples safely to Earth. It then went on to make a flyby of
comet Tempel 1. In 2005 an even more ambitious mission was launched. Deep Impact
was equipped with a probe that would be sent on a collision course with Comet
Tempel 1. The probe successfully crashed into the comet in July of that year.

Amazing image of the surface of comet 67P

Rosetta Mission

The Rosetta spacecraft was launched in 2004 on a 10 year mission to catch up with the comet 67P, enter into orbit, then launch a probe onto its surface. In order to achieve such an extraordinary feat the spacecraft would have to initially travel a total of 4 billion miles, involving several orbital slingshots from the inner planets of the solar system, this objective alone was a logistical task on an enormous scale.

Incredibly this task was achieved and in August of 2014 the second phase of the mission was also completed successfully as the Rosetta spacecraft entered into orbit around the comet, a first in space exploration. Three months later in November 2014 Rosetta deployed the Philae lander on its journey towards the comet. Scientists at the European Space Agency held their breath as they waited for news on its fate. Initially it was thought that Philae had made a textbook landing on the comet’s surface but hours later it was revealed that it had bounced twice before landing on its side against a cliff.

Unfortunately this meant that Philae would only have a short lifespan as it would not be able to receive enough sunlight to keep its batteries going. It was still able to capture some extraordinary images of the comet’s surface and undertake many scientific experiments. The European Space Agency still hold out hope that Philae may be able to receive more sunlight in the near future and wake up from its standby mode.

Missions to the Kuiper Belt

New Horizons

Launch: January 2006Arrival: July 2015Agency: NASASummary: After its visit to Pluto NASA is hoping to extend the New Horizons mission
to investigate one or maybe two other Kuiper Belt Objects. Mission
controllers will search for objects near the craft's flight path that have
diameters between 50 to 100 kilometers for a possible flyby.